Grow better. Get a CO2 grow room calculator & grow calendar

Your plants need carbon dioxide. So it’s logical that they could benefit from additional CO2 enrichment. This is the point where many growers go looking for a CO2 grow room calculator.


When you grow cannabis indoors, you’re always on the lookout for new and ingenious ways to dial in your grow.


It takes dedication to continually optimise your grow space in pursuit of growing top quality plants.


And it’s always a challenge trying to balance the cost of the potential rewards vs the costs of the improvements to you and the environment.


I could go down the rabbit hole and dive deep into the equipment and set up you’ll need if you want to supplement CO2. CO2 generators, CO2 bags etc…


But that’s another post entirely and for the purposes of this post, I’ll specifically be discussing:


  • How a CO2 grow room calculator can help you.
  • What a CO2 grow room calculator can’t do for you.
  • How to use our environmental calendar.
  • How to use our CO2 grow room calculator.


You want to uncover how much CO2 you should be supplementing (and when!) to get the maximum benefits. But there’s so much information available.


Doing the research (before even implementing it!) can seem like a huge task!


So we’re going to solve that problem for you here, today.


Disclaimer: Any information given on this site is for educational purposes only. Please ensure if you’re growing cannabis you’re doing so in accordance with the law and subject to appropriate permissions and licenses of the applicable country.


CO2 grow room calculators work out the CO2 flow rate


How a CO2 grow room calculator can help you:


The purpose of a CO2 grow room calculator is to calculate how much CO2 you’ll need to add to your grow space to bring the ppm (parts per million) of CO2 up to the optimum level.


A CO2 grow room calculator works out the CO2 flow rate in cubic meters per hour.


The CO2 flow rate is how fast the volume of CO2 passes from the CO2 tank or source, through the valve into your grow space.


You need to know what to adjust this to, to get the right amount of CO2 in your grow space for your given situation, at any given time.


A CO2 grow room calculator is helpful if you’re planning on supplementing and removes the need for mental gymnastics. 👌


What a CO2 grow room calculator can’t do for you.


A CO2 grow room calculator can’t tell you how regularly you need to top up your room with CO2.


This is because there’s no way to know how much CO2 your plants will use, or how much CO2 might leak out of your grow space.


The solution to this, is normally to just ‘top up’ the grow space with CO2 for a given amount of time every hour – 15 minutes per hour for example.


CO2 grow room calculators also don’t take into consideration that there are optimal levels of CO2 for each different stage of your plant’s life cycle.


They rely solely on you inputting the appropriate target level of CO2. Then the calculator can tell you the flow rate you need, for the length of time you’ve chosen to dose your grow space with CO2 each hour.


One thing’s for sure. You certainly don’t need to be providing the ‘recommended optimum 1500 ppm’ all the time from day one. And if you do, you are just wasting money and resources.


A CO2 calculator also won’t factor in what lights you’re using – which is key! (Checkout this post for more info on how CO2, light and temperature interact!)


Because the amount of carbon dioxide that your particular plants, in your particular grow space need is dependent on a number of factors… There’s no one size that fits all recommendations.


But we’ve gone one better!


We’ve updated our ultimate VPD calculator and environmental timeline to include information relevant to you if you’re looking to supplement your grow space with CO2. 🙌


You can now use our CO2 grow room calculator alongside your own unique customisable environmental timeline to boost your grow with additional CO2.


VPD chart illustration


How to use our environmental calendar.


1. First get access to your FREE VPD calculator and environmental timeline here.


2. Populate it with all the info about your own specific grow circumstances by adjusting your ‘Timeline settings.’


3. Make sure you select an answer to the question ‘Are you supplementing with CO2?


4. Then pay particular attention to the row in the environmental calculator that relates to CO2 Levels.


5. This row gives you the CO2 ppm levels you need to aim for, at any time, specific to your unique grow!


6. These ppm figures are what you enter into the box called ‘Target CO2 Level (ppm)’ within the CO2 grow room calculator. (More about that shortly!)


7. Check back in with your environmental timeline every week, and see what if any amends need to be made to the amount of CO2 you’re supplementing.


8. When you need to adjust the CO2 levels, put the new target CO2 ppm figures into the CO2 grow room calculator. Adjust your CO2 supplementation accordingly!


The figures that our environmental calculator generates for temperature, humidity, VPD, PPFD and CO2 etc, are a product of complex calculations.


These calculations factor in how the following things will affect your grow:


  • Whether you’re growing from seed or clone.
  • What type of plants you’re growing.
  • What types of lights you using (for both veg and flowering.)


And then give recommendations on all of the following things in addition to the ideal CO2 ppm for supplementation:


  • Day and night VPD.
  • Daytime leaf surface temperatures.
  • Ambient day and night relative humidities.
  • For each and every week, for the duration of your grow cycle.


Which is why it’s such a useful resource!!


Now let’s take a look at how to use our CO2 grow room calculator….


CO2 grow room calculator


How to use our CO2 grow room calculator


The point of a CO2 grow room calculator is to enable you to understand how much CO2 you should be supplementing in your grow, at any given time, to get the greatest benefits.


To use our CO2 grow room calculator you’ll need to know:


1. The dimensions of your grow space.


2. How much CO2 you need to add to your grow space in ppm.


The amount of CO2 you need in your grow area is (substantially) different for every stage of your plant’s growth cycle.


But hopefully you’re armed with this info now, having got your hands on our ultimate environmental calculator.


Let’s take early flower as an example, as that’s when the highest levels of additional CO2 are beneficial. (Checkout this post about supplementing CO2 in flowering stage when growing indoors.)


There’s 400 ppm of CO2 present at normal atmospheric conditions. The recommended maximum ppm for CO2 during flowering when cultivating cannabis is 1,500 ppm.


The calculator works out the difference, and this means that you need to add 1,100 ppm of CO2 to get the optimal level in your grow space.


You then need to fill in how many minutes out of every hour you are going to be adding CO2 to your grow space.


The length of time that you’re adding CO2 from your canister into your grow area influences the flow rate.


If you add CO2 to your grow area over a long period of time, the rate at which you’re adding it can be less.


When you add your CO2 over a shorter time, the flow rate will need to be higher to get the right amount of CO2 into the grow space in a shorter time frame.


When you put your own details into the calculator, it generates the CO2 flow rate that you need to use, to ensure you’ll maintain the right CO2 levels for your plants throughout the day.


Handy tips:


1. If you want to supplement your grow environment with CO2, it’s really important to ensure that you’ve optimised everything else within your grow space first.


2. For a lot of growers, making tweaks to the grow space in preparation for being ready for supplementing CO2, will in itself give good results and returns in the form of increased yields.


3. You can then build on those good results when supplementing CO2, leading to further increased yields and product quality.


4. It’s a good idea to ensure your plants have no pest problems or nutrient issues too before you start adding CO2.


5. Supplementing CO2 before laying the groundwork risks you wasting money and resources, without reaping the potential rewards.


6. Remember that your plants can only make use of supplemental CO2 during daylight hours when they’re actively photosynthesising.


7. You can use a CO2 controller. But the best way to manage the uncertainty about levels of CO2 in your grow environment is to actually have a CO2 monitor in there to continually take readings.


8. Checkout these other related posts to upgrade your grow knowledge: What’s the ideal grow room temp with CO2? CO2 in flowering stage. Why supplement when growing indoors. 5 Ways vapour pressure deficit can improve your indoor grow.


Optimise your grow space before supplementing with CO2




It’s important to note that every grow room or space will be sealed to different levels, and will contain different numbers of and different types of plants.


Therefore use our CO2 grow room calculator as a guide.


Your space could be really well sealed and you might only have a couple of plants in there to use the CO2 you’re supplementing.


If that’s the case… CO2 levels in your grow space may be higher than your chosen target CO2 level if you supplement at the recommended flow rate.


Your grow room or tent could equally be a little on the leaky side, and choc full of plants.


If that’s the case… Your CO2 levels inside may be lower than your chosen target CO2 level if you supplement at the recommended flow rate.


Use a grow room monitor to take continuous, accurate CO2 readings. It’ll enable you to optimise your grow space to an even higher level.


The Grow Sensor not only measures CO2, but temperature, humidity, VPD and light intensity.


The sensor sends data to the Grow Sensor App, and this in turn feeds back to you.


Just think what a well oiled machine of a grow setup you could have if you just had real time feedback on all these measurements! 🤯


You can sign up to get early access here!


Improving the efficiency of your grow setup by using these the Grow Sensor and app together will save you time, stress AND money.


All whilst improving your grow’s efficiency, reducing waste and therefore minimising the impact of your grow on the environment. 😇

Get your free CO2 calculator

Grow the best plants now with your FREE CO2 grow room calculator.

    Author avatar
    Lucy Starley
    Co founder at Grow Sensor - the smart grow room monitor. Lover of art, animals, sewing, walking and mushroom hunting. Inbound marketing expert and expert tea drinker. Lucy is currently open for Guest posts.

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